This invention is directed to a peroxide-curable brominated or iodinated fluoroelastomer composition that contains an N,N,N',N'-tetrasubstituted 1,8-diaminonaphthalene that functions as a mold release agent, accelerates the rate of cure of the polymer and does not detrimentally affect the physical properties of the polymer.
Peroxide-curable vinylidene fluoride based fluoroelastomers that contain units derived from brominated olefins have been favorably accepted by the industry. These fluoroelastomers when peroxide cured have good resistance to damage by heat, solvents and corrosive chemicals and they are characterized by being especially resistant to degradation by steam. However, the manufacture of molded products made from these polymers has presented a serious problem because the vulcanizates tenaciously adhere to the walls of the mold cavity, in spite of the fact that mold release agents are sprayed on the mold cavity or incorporated in the polymer, and the shaped product is frequently torn or damaged when removed from the mold. Also, the incorporation of a mold release agent into the polymer can, and usually does, have serious adverse effects on the physical and cure properties of the vulcanizate, for example, Mooney Scorch and compression set, which can limit the successful commercial use of the polymer. Deposits of polymer on the mold cavity surface and poor release of the shaped vulcanizate from the mold are major reasons for rejecting the shaped article which, of course, adds to the expense of manufacture of such molded articles. The corresponding peroxide-curable fluoroelastomer compositions that contain units derived from an iodinated olefin do not have as serious a problem of vulcanizate tearing when removed from metal mold cavities as do the fluoroelastomer compositions containing brominated olefin cure-sites. However, the rate of cure of the fluoroelastomer compositions having iodinated olefin cure sites can be accelerated using the fluoroelastomer compositions of the present invention, and rapid cure is especially important when the fluoroelastomer composition is used in injection molding operations. The present invention provides a peroxide-curable fluoroelastomer composition containing an N,N,N',N'-tetrasubstituted 1,8-diaminonaphthalene that does not stick to the metal mold cavity and tear when ejected or removed from the mold cavity while, at the same time, the incorporation of the aromatic diamine into the polymer does not detrimentally affect its important physical properties and, furthermore, the rate of cure of the fluoroelastomer is accelerated.